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[3.8] bpo-44689: ctypes.util.find_library() now finds macOS 11+ system libraries when built on older macOS systems (GH-27251) #28054

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merged 1 commit into from Aug 30, 2021
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[3.8] bpo-44689: ctypes.util.find_library() now finds macOS 11+ system libraries when built on older macOS systems (GH-27251) #28054

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5 changes: 5 additions & 0 deletions Misc/NEWS.d/next/macOS/2021-07-20-22-27-01.bpo-44689.mmT_xH.rst
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@@ -0,0 +1,5 @@
:meth:`ctypes.util.find_library` now works correctly on macOS 11 Big Sur
even if Python is built on an older version of macOS. Previously, when
built on older macOS systems, ``find_library`` was not able to find
macOS system libraries when running on Big Sur due to changes in
how system libraries are stored.
29 changes: 26 additions & 3 deletions Modules/_ctypes/callproc.c
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Expand Up @@ -1447,14 +1447,37 @@ copy_com_pointer(PyObject *self, PyObject *args)
return r;
}
#else

#ifdef __APPLE__
#ifdef HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH
#define HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH_RUNTIME \
__builtin_available(macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0, *)
#else
// Support the deprecated case of compiling on an older macOS version
static void *libsystem_b_handle;
static bool (*_dyld_shared_cache_contains_path)(const char *path);

__attribute__((constructor)) void load_dyld_shared_cache_contains_path(void) {
libsystem_b_handle = dlopen("/usr/lib/libSystem.B.dylib", RTLD_LAZY);
if (libsystem_b_handle != NULL) {
_dyld_shared_cache_contains_path = dlsym(libsystem_b_handle, "_dyld_shared_cache_contains_path");
}
}

__attribute__((destructor)) void unload_dyld_shared_cache_contains_path(void) {
if (libsystem_b_handle != NULL) {
dlclose(libsystem_b_handle);
}
}
#define HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH_RUNTIME \
_dyld_shared_cache_contains_path != NULL
#endif

static PyObject *py_dyld_shared_cache_contains_path(PyObject *self, PyObject *args)
{
PyObject *name, *name2;
char *name_str;

if (__builtin_available(macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0, *)) {
if (HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH_RUNTIME) {
int r;

if (!PyArg_ParseTuple(args, "O", &name))
Expand Down Expand Up @@ -1998,7 +2021,7 @@ PyMethodDef _ctypes_module_methods[] = {
{"dlclose", py_dl_close, METH_VARARGS, "dlclose a library"},
{"dlsym", py_dl_sym, METH_VARARGS, "find symbol in shared library"},
#endif
#ifdef HAVE_DYLD_SHARED_CACHE_CONTAINS_PATH
#ifdef __APPLE__
{"_dyld_shared_cache_contains_path", py_dyld_shared_cache_contains_path, METH_VARARGS, "check if path is in the shared cache"},
#endif
{"alignment", align_func, METH_O, alignment_doc},
Expand Down